Wireless transmissions between a base station and one or more user equipment (UE) within a cell are generally dynamically scheduled in each subframe or slot. For example, the base station may assign resources (e.g., time-frequency resources) for downlink transmissions to one or more UEs and grant the use of resources for uplink transmissions from one or more UEs. The downlink assignments and uplink grants may be provided to the UEs via a physical downlink control channel (PDCCH).
For Multiple Input Multiple Output (MIMO) communications, each UE may be assigned a rank indicating the number of layers or data streams utilized by the base station to transmit downlink data to the UE. Within a subframe or slot, the rank assigned to a UE is generally preserved between scheduled sub-bands or resource block groups of the subframe or slot. However, if the traffic in the cell is bursty, maintaining the same rank for each UE across scheduled sub-bands of a subframe or slot may result in inefficient utilization of the downlink resources.